Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.27	13.857%	$187.0329	$187.03	$187.05	$187.00
Purchase #2	$41.90	6.766%	$44.735	$44.74	$44.75	$44.70
Purchase #3	$115.34	10.549%	$127.5072	$127.51	$127.50	$127.50
Purchase #4	$217.63	6.791%	$232.4093	$232.41	$232.40	$232.40
Purchase #5	$196.73	11.733%	$219.8123	$219.81	$219.80	$219.80
Purchase #6	$38.98	10.226%	$42.9661	$42.97	$42.95	$43.00
Purchase #7	$248.43	3.352%	$256.7574	$256.76	$256.75	$256.80
7 purchase totals =	$1,023.28		$1,111.2202	$1,111.23	$1,111.20	$1,111.20